SQLite

int sqlite3VdbeSorterInit(
  sqlite3 *db,                    /* Database connection (for malloc()) */
  int nField,                     /* Number of key fields in each record */
  VdbeCursor *pCsr                /* Cursor that holds the new sorter */
){
  int pgsz;                       /* Page size of main database */
  int i;                          /* Used to iterate through aTask[] */

  VdbeSorter *pSorter;            /* The new sorter */
  KeyInfo *pKeyInfo;              /* Copy of pCsr->pKeyInfo with db==0 */
  int szKeyInfo;                  /* Size of pCsr->pKeyInfo in bytes */
  int sz;                         /* Size of pSorter in bytes */
  int rc = SQLITE_OK;
#if SQLITE_MAX_WORKER_THREADS==0
# define nWorker 0

    pSorter->db = db;
    for(i=0; i<pSorter->nTask; i++){
      SortSubtask *pTask = &pSorter->aTask[i];
      pTask->pSorter = pSorter;
    }

    if( !sqlite3TempInMemory(db) ){
      i64 mxCache;                /* Cache size in bytes*/
      u32 szPma = sqlite3GlobalConfig.szPma;
      pSorter->mnPmaSize = szPma * pgsz;

      mxCache = db->aDb[0].pSchema->cache_size;
      if( mxCache<0 ){
        /* A negative cache-size value C indicates that the cache is abs(C)
        ** KiB in size.  */
        mxCache = mxCache * -1024;
      }else{
        mxCache = mxCache * pgsz;
      }
      mxCache = MIN(mxCache, SQLITE_MAX_PMASZ);
      pSorter->mxPmaSize = MAX(pSorter->mnPmaSize, (int)mxCache);

      /* EVIDENCE-OF: R-26747-61719 When the application provides any amount of
      ** scratch memory using SQLITE_CONFIG_SCRATCH, SQLite avoids unnecessary
      ** large heap allocations.
      */
      if( sqlite3GlobalConfig.pScratch==0 ){
        assert( pSorter->iMemory==0 );

do_execsql_test 1.2 {
  CREATE INDEX i1 ON t1(b);
}

db close
tvfs delete

#-------------------------------------------------------------------------
# Test that the PMA size is determined correctly. The PMA size should be
# roughly the same amount of memory allocated to the main pager cache, or
# 250 pages if this is larger.
#
testvfs tvfs
tvfs script tv_callback
tvfs filter {xOpen xWrite}

proc tv_callback {method args} {
  global iTemp
  global F
  switch $method {
    xOpen {
      if {[lindex $args 0]==""} { return "temp[incr iTemp]" }
      return "SQLITE_OK"
    }

    xWrite {
      foreach {filename id off amt} $args {}
      if {[info exists F($id)]==0 || $F($id)<($off + $amt)} {
        set F($id) [expr $off+$amt]
      }
    }
  }
}

catch { db close }
forcedelete test.db
sqlite3 db test.db -vfs tvfs
execsql { CREATE TABLE t1(x) }

# Each iteration of the following loop attempts to sort 10001 records
# each a bit over 100 bytes in size. In total a little more than 1MiB 
# of data.
#
breakpoint
foreach {tn pgsz cachesz bTemp} {
  2 1024   1000  1

  1 4096   1000  0
  2 1024   1000  1

  3 4096  -1000  1
  4 1024  -1000  1

  5 4096  -9000  0
  6 1024  -9000  0
} {
  do_execsql_test 2.$tn.0 "
    PRAGMA page_size = $pgsz;
    VACUUM;
    PRAGMA cache_size = $cachesz;
  "

  do_test 2.$tn.1 {
    set ::iTemp 0
    catch { array unset F }
    execsql {
      WITH x(i, j) AS (
        SELECT 1, randomblob(100)
        UNION ALL
        SELECT i+1, randomblob(100) FROM x WHERE i<10000
      )
      SELECT * FROM x ORDER BY j;
    }
    expr {[array names F]!=""}
  } $bTemp
}

finish_test